Add authors pages and requestType notifications

Introduce full authors browsing/detail feature and enhance notifications to support type-specific titles.

- Add server APIs: authors search, author detail, and author books routes (audnexus integration) that require auth and enrich results with library matches.
- Add frontend pages/components: /authors listing and /authors/[asin] detail pages; AuthorCard, AuthorGrid, AuthorDetailCard, SimilarAuthorsRow, and related skeletons.
- Add hook and integration stubs: new useAuthors hook and audnexus-authors integration; update audible service to expose audibleBaseUrl.
- Update AudiobookDetailsModal to use audibleBaseUrl and link author names to author detail pages.
- Add header navigation link to Authors.
- Notifications: extend docs and code to include requestType (audiobook|ebook), add getEventTitle/getEventMeta helpers, update queue signature and providers/processors/tests to pass/handle requestType so titles can be resolved per request type.
- Misc: job queue, processors, provider tests and notification tests updated to reflect new behavior.

This change enables browsing authors and provides type-aware notification titles without per-provider changes.

src/lib/services/notification/providers/discord.provider.ts

@@ -4,7 +4,7 @@
  */
 
 import { INotificationProvider, NotificationPayload, ProviderMetadata } from '../INotificationProvider';
-import { getEventMeta, type NotificationSeverity } from '@/lib/constants/notification-events';
+import { getEventMeta, getEventTitle, type NotificationSeverity } from '@/lib/constants/notification-events';
 
 export interface DiscordConfig {
   webhookUrl: string;
@@ -59,8 +59,9 @@ export class DiscordProvider implements INotificationProvider {
   }
 
   private formatEmbed(payload: NotificationPayload): any {
-    const { event, title, author, userName, message, requestId, timestamp } = payload;
+    const { event, title, author, userName, message, requestId, requestType, timestamp } = payload;
     const meta = getEventMeta(event);
+    const resolvedTitle = getEventTitle(event, requestType);
 
     const isIssue = event === 'issue_reported';
     const fields = [
@@ -74,7 +75,7 @@ export class DiscordProvider implements INotificationProvider {
     }
 
     return {
-      title: `${meta.emoji} ${meta.title}`,
+      title: `${meta.emoji} ${resolvedTitle}`,
       color: SEVERITY_COLORS[meta.severity],
       fields,
       footer: {